Biomechanics and Medicine in Swimming XI

Effects of Recently Developed Swimwear on Drag
During Front Crawl Swimming
ogita, F., huang, Z., Kurobe, K., ozawa, G., taguchi,t.,
tanaka, t.
National Institute of Fitness and Sports, Japan
The effect on active drag of 3 new types of swimwear compared to conventional
wear was investigated in 8 male subjects swimming at different
velocities to establish the drag-velocity relationship. The active drag
force was directly measured during front crawl swimming using a system
of underwater push-off pads instrumented with a force transducer.
When mean drag values were estimated for a range of swimming speed
(1.2 to 1.8 m•s-1 Figure 1. Swimwear
A
used in this
B
experiment.
C D
Figure 1. Swimwear
A B
used in this
B C
experiment.
C D
A;
A;
a
conventional
conventional
swimwear
swimwear
B,
B,
C,
C,
D;
D;
new
new
types
types
of
of
swimwear
swimwear
developed
developed
in
in
2008
2008
by
by
different
different
manufactures
manufactures
Measurement of active drag; The measurements were performed with a modified
MAD system similar to that described by Toussaint et al. (1988b) (Figure 2). The
Measurement system similar of to active that drag; described The measurements by Toussaint et were al. performed (1988b) (Figure with 2). The
essential aspects of the apparatus and the accuracy of the collected data have been
), statistically non-significant drag reduction effects of a modified aspects of MAD the apparatus system similar and the to that accuracy described of the by collected Toussaint data et al. have been
previously described in detail (Ogita et al., 2004, 2006, Toussaint et al., 1988b). The
1-5 N (2-6%) were observed for the new types of swimwear. Even if no system
(1988b) described
allowed
(Figure in
the swimmer
2). detail The (Ogita
to
essential et al.,
push off
aspects 2004,
from fixed
of 2006, the
pads
apparatus Toussaint
at each stroke.
and et al., the 1988b).
The
ac- The
system allowed the swimmer to push off from fixed pads at each stroke. The 15 push-
major differences in drag were found among swimwear, our results sugoff
pads Figure curacy were 1. Swimwear of fixed the A
1.30 collected used m in this apart
Bdata experiment. on have a 23 been m
C
horizontal previously D
rod, described and the in rod detail
off pads were fixed 1.30 m apart on a 23 m horizontal rod, and the rod was mounted
gest that the observed reduction, even if non significant, could indeed 0.75m (Ogita below A; a conventional the et al., water 2004, surface. swimwear 2006, The Toussaint rod was et instrumented al., 1988b). with The system a force transducer allowed
0.75m below at one
B, C, the D; new water types surface. of swimwear The developed rod was in instrumented 2008 by different with manufactures a force transducer at one
explain the observed competitive advantage.
end of the swimmer swimming to pool push to off measure from fixed the push-off pads at each forces. stroke. The The force 15 signal push-
end of the swimming pool to measure the push-off forces. The force signal was lowpass
Measurement filtered off pads (30-Hz were of active fixed cut-off drag; 1.30 frequency), The m apart measurements on on-line a 23 m digitized were horizontal performed at 100-Hz rod, with and sampling a the modified rod
pass filtered (30-Hz cut-off frequency), on-line digitized at 100-Hz sampling rate, and
Key words: active drag, swimwear, MAd system, swimming perfor- MAD stored system
stored was on the mounted similar hard disk to
hard disk 0.75m that of the described
of the below notebook the by water computer. Toussaint
computer. surface. et The The al. force (1988b)
force rod was signal (Figure
signal instrumented pushed 2). off The
pushed off from the
essential
mance
second with aspects to the a force last of the
last (15th) transducer apparatus pad at was and
was one time the
time end accuracy integrated, of the swimming of and the collected
and yielded pool to the data
the measure average have
average the been force. The
previously mean velocity described
velocity was in
was computed detail (Ogita
computed from et al.,
from the 2004,
the time 2006,
time taken Toussaint
taken to cover et
cover the al.,
the distance 1988b).
distance between The
push-off forces. The force signal was low-pass filtered (30-Hz cut-off between the
system allowed the swimmer to push off from fixed pads at each stroke. The 15 push- the
IntroductIon
second frequency), and last pad on-line (i.e.13 digitized x 1.3 = at 16.9 100-Hz m). sampling For the drag rate, and measurement, stored on the
the subject
off pads were fixed 1.30 m apart on a 23 m horizontal rod, and the rod was mounted subject
performed only arm stroke (without leg kicking), and the legs were supported and fixed
Recently (2008-2009), numerous new world records were made in com0.75m
performed below hard the only disk water arm of surface. the stroke notebook (without The rod computer. was leg instrumented kicking), The force and with the signal a legs force pushed were transducer supported off from at one and fixed
petitive swimming. The great success has been considered to be in part end of the the swimming second to pool the to last measure (15th) the pad push-off was time forces. integrated, The force and signal yielded was the low-
attributed to a reduction in drag associated with advances in the quality pass filtered average (30-Hz force. cut-off The frequency), mean velocity on-line was digitized computed at 100-Hz from the sampling time taken rate, and to
of swimwear.
stored on cover the hard the disk distance of the between notebook the computer. second The and force last pad signal (i.e.13 pushed x 1.3 off from = 16.9 the
second to
Drag consists of skin friction, pressure drag, and wave-making resis- m). the For last the (15th) drag pad measurement, was time integrated, the subject and yielded performed the average only arm force. stroke The
mean velocity was computed from the time taken to cover the distance between the
tance, and total drag equals to the sum of those factors (Toussaint et al., (without leg kicking), and the legs were supported and fixed together by
second and last pad (i.e.13 x 1.3 = 16.9 m). For the drag measurement, the subject
2000). Previously, it was assumed that friction drag was negligible (5% the same pull buoy (buoyant force 15.7N).
performed only arm stroke (without leg kicking), and the legs were supported and fixed
of total drag) given the high Reynolds numbers (>105) that occur during
swimming (Toussaint et al., 1988b). However, later Waring (1999) sug- Figure
Figure
2.
2.
Schematic
Schematic
side
side
view
view
of
of
system
system
to
to
measure
measure
active
active
drag
drag
(MAD
(MAD
system)
system)
used
used
in
in
this
this
study.
study.
gested that a significant reduction in total drag could be accomplished
by reducing pressure drag by the use of vortex generators minimizing
separated flow.
Over the last decade, swimwear manufacturers have tried further
development of special fabrics and surface treatments of swimwear
which supposedly reduce drag. The manufacturer which has developed
the swimwear used by the most swimmers in the Beijing Olympics
claimed that swimmers can reduce (passive) drag by 10% when wearing
the new type of swimwear. However, it is probably incorrect to assume
that results obtained by passive measurement are directly applicable to
those by active measurement (Toussaint et al., 2000). Therefore, in the
present study, the total active drag obtained when wearing new types of
swimwear were compared to those evoked when wearing conventional
swimwear.
Methods
Subjects; The subjects were 8 well-trained male college swimmers.Their
mean (±SD) age, height, body mass, and maximal oxygen uptake (VO-
2
max) were 20(±1) yrs, 1.68 (±0.04) m, 64.0 (±5.2) kg, 4.17(±0.36)
l•min -1 , and 65.8 (±4.7) ml•kg -1 •min -1 , respectively. Each subject was
fully informed of the purposes, protocol, and procedures of this experiment,
and any risks, and voluntarily participated in this study.
Swimwear; To evaluate the effects of differences in swimwear on total
drag, a conventional swimwear (box type: A) and 3 new types of swimwear
(long type: B, C, D) which was developed in 2008 were used in this
experiment (see Figure 1).
(±0.04) m, 64.0 (±5.2) kg, 4.17(±0.36) l•min
chaPter3.PhysioLogyandBioenergetics
-1 , and 65.8 (±4.7) ml•kg -1 •min -1 age, height, body mass, and maximal oxygen uptake (VO2max) were 20(±1) yrs, 1.68
(±0.04) m, 64.0 (±5.2) kg, 4.17(±0.36) l•min ,
respectively. Each subject was fully informed of the purposes, protocol, and procedures
of this experiment, and any risks, and voluntarily participated in this study.
Swimwear; To evaluate the effects of differences in swimwear on total drag, a
conventional swimwear (box type: A) and 3 new types of swimwear (long type: B, C,
D) which was developed in 2008 were used in this experiment (see Figure 1).
-1 , and 65.8 (±4.7) ml•kg -1 •min -1 55 ,
respectively. Each subject was fully informed of the purposes, protocol, and procedures
of this experiment, and any risks, and voluntarily participated in this study.
drag obtained Swimwear; when To wearing evaluate new the types effects of swimwear of differences were compared in swimwear to those on evoked total drag, a
when conventional wearing conventional swimwear swimwear. (box type: A) and 3 new types of swimwear (long type: B, C,
D) which was developed in 2008 were used in this experiment (see Figure 1).
METHODS
Subjects; The subjects were 8 well-trained male college . swimmers. Their mean (±SD)
age, height, body mass, and maximal oxygen uptake (VO2max)
were 20(±1) yrs, 1.68
(±0.04) m, 64.0 (±5.2) kg, 4.17(±0.36) l•min -1 , and 65.8 (±4.7) ml•kg -1 •min -1 ,
respectively. Each subject was fully informed of the purposes, protocol, and procedures
of this experiment, and any risks, and voluntarily participated in this study.
Swimwear; To evaluate the effects of differences in swimwear on total drag, a
conventional swimwear (box type: A) and 3 new types of swimwear (long type: B, C,
D) which was developed in 2008 were used in this experiment (see Figure 1).
Figure 2. Schematic side view of system to measure active drag (MAD system) used in this study.
To measure drag and to establish the relationship between drag and
swimming velocity, the subjects were asked to swim 25 m more than
10 times at different but constant velocities (range 0.80-1.90 m•s -1 ). At
constant swimming velocity the mean propulsive force is equal to the
mean drag force (Fd) (Toussaint 1988b). On each trial, mean Fd and
mean swimming velocity (v) were calculated. These v and Fd data were
least-squares fitted to the function:
Fd = A•vn
where, A and n are constants of proportionality, and were respectively
adopted as drag coefficient and drag exponent in this study.
All subjects used the same 4 types of swimwear (i.e. one conventional
and 3 new, developed in 2008), and the order of testing of each
swimwear was randomized. All measurements for each subject were
completed in the same day.
Evaluation of effect on drag; The A and n obtained with each swimwear
were computed for each subject. These fitted functions were used
to estimate the drag at three different velocities (1.2, 1.5, 1.8 m•s -1 ). The
effect on drag was evaluated by comparing the estimated drag among 4
types of swimwear. Intra-individual differences (in %) with respect to
the drag when wearing conventional swimwear were also calculated at
the three velocities studied.
Statistics; All data were expressed by mean and SD or individual
value. Two-way analysis of variance with repeated measures was used
to test the difference in estimated drag values among 4 conditions by
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